Any idea why?

I doning in-situ hybridization in section detection MYC mRNA. I am
geting signal in the cytoplasm as well as spot in the nucleus of some
cells. Is any body know why I am getting signal in nucleus if we know
that the mature mRNA in the cytoplasm. Beside that the probes I am
used is olignucleotide and design specifically for mRNA only. Any help
will be appreciated.
Majde